The present invention relates to an improvement in means for shifting gears on dual shift bicycles, i.e., bicycles having two sets of sprocket clusters and means for shifting the drive chain between the sprockets thereof. Such bicycles generally are designed to operate at various gear ratios (speeds), such as 10, 12, 15 etc.
The dual shift bicycles in use today have two shift handles, one for each of the front and rear derailleur mechanisms, and are cumbersome and difficult to operate. The two handles are interactive and must be manipulated in a manner that is beyond the knowledge and skill of the average operator (bike rider). The bike rider must operate either or both of the gear selection handles in order to shift the bicycle to the desired gear ratio. The two handles must be adjusted further after the shift is completed, such further adjustment generally being made by ear while listening for rubbing and/or grinding of the drive chain. It is extremely difficult for the operator to remember which handle or handles are to be operated to place the gear shift in the desired one of the ten different gear ratios and the operator must also consider whether he is shifting up or down and remember which gear he is in prior to the shifting operation.
In my prior patent, U.S. Pat. No. 4,412,828, there is disclosed a control means for shifting gears on dual shift bicycles that is easy to operate and is constructed so that the front and rear derailleurs are controlled together to shift to any selected gear from any engaged gear with a single operator action. Accordingly, the operator need not concern himself with which one or both of the derailleurs is to be shifted, which direction to shift the derailleurs, or how much the derailleurs are to be shifted. Also, there is provided a pre-select feature that allows the operator to anticipate and select the next gear change while continuously pedaling in the present gear. The actual gear change can be postponed by the operator indefinitely or can be overridden by a different subsequent selection if desired. Furthermore, the control means operates to directly position both front and rear derailleurs for the selected gear without any back and forth shifting for intermediate gears. This allows for the fastest possible shift between any two gears. A feature of the control means is that shifting can take place with both hands of the operator (bicycle rider) on the handle bars to provide increased safety and better control. Furthermore, the selection and control means are designed to facilitate a rapid series of down shifts. (Rapid down shifting, for example, as needed for efficient hill climbing). Such a series of down shifts can be made without intervening gear selections between shifts.
In the achievement of the above-described ends, the mechanism indicates the gear presently engaged or preselected by the operator, i.e., gear ratios (speeds) 1-10 for a ten speed bicycle, and provide for simple, error free shifting into any selected higher or lower gear. The bicycle rider need not be concerned with calculating or memorizing any shifting sequence.
It is the general object of the present invention to provide an improvement over the shift control mechanism disclosed in my prior patent. Briefly, the shift control mechanism of the present invention includes the following improvements over the prior design:
(1) There are no modifications required to the standard type of derailleurs in use today. PA1 (2) The design uses standard stranded control cables. PA1 (3) The mechanism is adjustable for use with various derailleur types and bicycle sizes. PA1 (4) The design is flexible such that it can be adapted easily for use with either "O.E.M." and aftermarket versions. PA1 (5) The design uses improved operator controls. PA1 (6) The design employs simplified cable routing. PA1 (7) The design involves improved operating margins for the shifter. PA1 (8) The design employs a simpler and smaller shifter.